Gas burner control approach

ABSTRACT

Various aspects of the invention relate to a control approach for gas burners. According to an example embodiment, calibration of gas burner control is carried out at predetermined points in time. A new stable calibration is established to replace a previous stable calibration in response to the burner operating under stable operating conditions for a predetermined period of time after the predetermined point in time. A preliminary calibration is established on the basis of most recent operating conditions in response to the burner operating under unstable operating conditions for the predetermined period of time.

FIELD OF THE INVENTION

The present invention relates to gas burner control, and more particularly, to approaches for gas burner control involving calibration.

BACKGROUND

Controllers and control methods for gas burners are provided for controlling the gas supply to the gas burner and are arranged between a gas supply source and the gas burner. In many applications, control approaches for gas burners have to be subjected to a calibration at specific points in time, e.g., after an installation of the control, a restart or reset of the burner. Up to now, gas burner control calibration has typically been subject to a waiting period to ensure a reliable or stable calibration of the control. If the burner varies from the stable operating conditions during the calibration or during the given time period, the calibration has typically been broken off and the burner controlled according to a previous setting or previous calibration. Unfortunately, the previous setting or previous calibration may no longer be correct due, e.g., to a change in gas quality or other condition. For example, if a previous calibration is from a different operating time (e.g., hours or days earlier), many conditions can change. Incorrect setting or calibration is often characterized by inadequate burner control.

SUMMARY

The present invention is directed to an approach for gas burner control that addresses challenges including those discussed above.

According to an example embodiment of the present invention, a gas burner control approach involves carrying out a calibration procedure, having a predetermined calibration point upon a predetermined point in time, to generate a calibration for the burner. If the burner operates under stable conditions during a predetermined time period after the predetermined point in time, the generated calibration is used to operate the burner. If the burner does not operate under stable conditions during the predetermined time, a preliminary calibration is carried out on the basis of recent operating conditions of the burner and used to operate the burner. In some instances, the generation of the calibration is broken off when the burner cannot be operated under stable operating conditions for the predetermined period of time after the predetermined point in time.

BRIEF DESCRIPTION OF THE FIGURES

In the following, the invention will be described generally in reference to example embodiments in combination with the attached drawings wherein:

FIG. 1 shows an approach to operating a gas burner with calibration, according to an example embodiment of the present invention.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration particular embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized, as structural and operational changes may be made without departing from the scope of the present invention.

According to an example embodiment of the present invention, a gas burner calibration procedure is carried out at a predetermined calibration point directly upon a predetermined point in time, without necessarily first operating the burner with previous calibration. The calibration is broken off when the burner cannot be operated under stable operating conditions for a predetermined period of time that is subsequent to the predetermined point in time. A preliminary calibration is carried out on the basis of most recent operating conditions and used to operate the gas burner.

If the calibration procedure is broken off because stable operating conditions cannot be achieved, the burner is set to a preliminary calibration value. This preliminary calibration value may be an intermediate value between a previous, stable calibration and a desired predetermined calibration point. In some instances, a desired calibration point used for carrying out the calibration (that did not led to stable operating conditions) is used to establish the preliminary calibration value. In other instances wherein the preliminary calibration value is established from the desired calibration point, the preliminary calibration is replaced with a previous stable calibration.

In various instances, an unsuccessful calibration (e.g., wherein stable operation over a predetermined time period is not achieved) is addressed by one or more of: using a previous stable calibration value; using a new calibration value (which resulted in unstable operation); or using a calibration value that is an intermediate value between a previous stable calibration value and the new calibration value.

Turning now to FIG. 1, at block 110, a calibration is generated for a burner at a predetermined calibration point, such as during the start-up of the burner or otherwise. If the burner operates under stable conditions for a predetermined time period at block 120, a previous calibration (if any) is replaced with the generated calibration and the burner is operated with the generated calibration. If the burner does not operate under stable conditions for the predetermined time period at block 120, a preliminary calibration is generated as a function of recent operating conditions at block 150. The burner is then operated with the preliminary calibration at block 160.

In some instances, the burner is operated with the generated calibration immediately after its generation at block 110. If the burner does not operate under stable conditions for the predetermined time period at block 120, the generated calibration is ceased to be used in operating the burner and, upon generation of the preliminary calibration at block 150, the generated calibration is replaced with the preliminary calibration.

In one instance, the calibration carried out at the predetermined calibration point is used if a specific part of a given calibration time has already expired when the calibration procedure is broken off (i.e., when unstable operation occurs). This course of action is selected, for example, if a satisfactory stable burner operation could be achieved over a large part of the intended calibration period.

In another instance, a previous stable calibration is used if a satisfactory stable operation can not be reached over a minimum period of time during a given calibration time. In this regard, a course of action can be pursued with an intermediate value between a desired predetermined calibration value and a previous stable calibration as discussed above.

In one instance, a calibration value determined at a predetermined time is used when a maximum period of time of a stable burner operation is reached. A previous stable calibration is used when a minimum period of time for a stable burner operation is not reached. An intermediate value between a previous stable calibration and the determined calibration value is used when the burner operates under stable conditions for a time period more than the minimum and less than the maximum.

In another example embodiment, a further criterion for the selection of suitable calibration values involves parameters characterizing the operation of the burner. In this regard, a variation range can, for instance, be fixed for a parameter characterizing the operation of the burner. If the selected parameter remains within this variation range, the calibration value generated at a desired predetermined calibration point can be used. If the parameter exceeds the given variation range, a previous stable calibration or preliminary calibration may be used (and, in some instances, a calibration procedure is reinitiated). As discussed above, an intermediate calibration value can also be implemented, with a value between a previous calibration value and the determined calibration value. For instance, if the variation range is small, the generated calibration value can be used; if the variation range is medium, an intermediate value between the previous stable and the new predetermined desired calibration can be used; and a previous calibration value can be used when a maximum variation range is exceeded.

If the calibration procedure is broken off and the burner is operated with a preliminary calibration, the calibration procedure can be repeated after a specific time period until a calibration on the basis of stable operating conditions can be reached.

In another embodiment, a gas burner control approach involves providing a gas-air mixture, namely, for supplying a gas flow and a combustion air flow to a burner. A calibration of the control is carried out at predetermined points in time such that the calibration is determined (and implemented) when, subsequent to the predetermined point in time, the burner has been operated under stable operating conditions for a predetermined time period, and the new calibration replaces previous calibration (if any). During the predetermined time period, the burner is immediately controlled with the calibration carried out at the predetermined point leading into the predetermined time period (e.g., not necessarily on the basis of a previous stable calibration). If the burner cannot be operated under stable operating conditions for the predetermined time period subsequently to the predetermined point in time, a preliminary calibration is carried out on the basis of the most recent operating conditions available. This preliminary calibration then replaces any current calibration. As soon as the control can carry out a stable calibration on the basis of stable operating conditions with a new calibration, the preliminary calibration is replaced by the new (stable) calibration.

The foregoing description of various embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention not be limited with this detailed description. 

1. A method for controlling gas burners for providing a gas-air mixture to a burner using a gas flow and a combustion air flow, the method comprising: generating a calibration for the burner at a predetermined calibration point and immediately using the generated calibration to operate the burner; in response to the burner operating for a predetermined period of time under stable operating conditions, continuing to operate the burner with the generated calibration; and in response to the burner operating under unstable operating conditions during the predetermined time period after the predetermined point in time, generating a preliminary calibration as a function of recent operating conditions of the burner and operating the burner with the preliminary calibration.
 2. The method of claim 1, further comprising, after operating the burner with the preliminary calibration, at another predetermined calibration point, regenerating a calibration and, in response to the burner operating for a predetermined period of time under stable operating conditions, replacing the preliminary calibration with the regenerated calibration and operating the burner with the regenerated calibration.
 3. The method of claim 1, wherein continuing to operate the burner with the generated calibration includes replacing a previous calibration with the generated calibration in response to the burner operating under stable conditions for the predetermined period of time after the predetermined calibration point.
 4. The method of claim 1, wherein generating a preliminary calibration as a function of recent operating conditions of the burner includes generating a preliminary calibration that has a value that is an intermediate calibration value between a previous calibration and the generated calibration.
 5. The method of claim 1, wherein generating a preliminary calibration as a function of recent operating conditions of the burner includes generating the preliminary calibration using operating conditions at the predetermined calibration point.
 6. The method of claim 1, further comprising, in response to the burner operating under unstable operating conditions during the predetermined time period, terminating the use of the generated calibration to operate the burner, generating the preliminary calibration as a function of recent operating conditions of the burner and operating the burner with the preliminary calibration.
 7. The method of claim 6, wherein the preliminary calibration is generated in response to the burner operating under unstable conditions after a specific portion of a given calibration time has elapsed.
 8. The method of claim 6, wherein generating a preliminary calibration as a function of recent operating conditions of the burner includes using a previous stable calibration as the preliminary calibration in response to the burner operating under unstable conditions before a specific part of the given calibration time has expired.
 9. The method of claim 1, wherein generating a preliminary calibration as a function of recent operating conditions of the burner includes using a previous stable calibration as the preliminary calibration.
 10. The method of claim 1, wherein generating a preliminary calibration as a function of recent operating conditions of the burner includes, in response to changes in a selected parameter that characterizes the operation of the burner being less than a specific measure for a predetermined period of time, using a predetermined calibration value as the preliminary calibration.
 11. The method of claim 1, further comprising, after operating the burner with the preliminary calibration, regenerating the calibration and operating the burner with the regenerated calibration until the burner operates for a predetermined period of time under stable operating conditions, and in response to the burner operating for a predetermined period of time under stable operating conditions with the regenerated calibration, replacing the preliminary calibration with the regenerated calibration and operating the burner with the regenerated calibration.
 12. A method for calibrating a gas burner, the method comprising: generating a calibration for the burner at a predetermined calibration point; operating the burner with the generated calibration; in response to the burner operating under stable operating conditions with the generated calibration for a predetermined time period, operating the burner with the generated calibration; and in response to the burner operating under unstable operating conditions with the generated calibration during the predetermined time period, generating a preliminary calibration as a function of recent operating conditions of the burner and operating the burner with the preliminary calibration.
 13. The method of claim 12, wherein generating a preliminary calibration as a function of recent operating conditions of the burner includes: in response to the burner operating under stable operating conditions for less than a minimum time period during the predetermined time period, using the previous calibration as the preliminary calibration; in response to the burner operating under stable operating conditions for more than a maximum time period during the predetermined time period, using the generated calibration as the preliminary calibration; and in response to the burner operating under stable operating conditions for more than the minimum time period but less than the maximum time period during the predetermined time period, using an intermediate calibration as the preliminary calibration, the intermediate calibration having a calibration value between a previous calibration and the generated calibration. 